Check out these FAQs about visiting the zoo during the July 4th weekend. I stay away the whole summer because it is too hot and crowded. Parking is a bear!
I missed the update, but Admission prices increased on December 15th, 2009 by $1. You can buy discounted tickets at Fiesta (by $2).
These days are still free: New Year's Day, Martin Luther King, Jr. Day, President's Day, Columbus Day, and the Friday after Thanksgiving
Did I mention that I stay away on free days, too, because of the crowds? I guess I am spoiled with my membership, which I paid $45 as a renewing member. With a Zoo membership I can go every day for with a charge!